Chiral Floquet Phases of Many-body Localized Bosons

TL;DR

This paper constructs and classifies chiral topological phases in driven many-body localized bosonic systems, revealing a quantized index linked to edge entropy flow and demonstrating the connection between bulk topology and edge chaos.

Contribution

It introduces exactly soluble models of chiral Floquet phases in MBL bosonic systems and classifies these phases via a quantized many-body index.

Findings

Chiral Floquet phases are classified by a quantized many-body index.

Nontrivial topology induces edge thermalization and chaos.

Models demonstrate stable chiral phases without symmetry requirements.

Abstract

We construct and classify chiral topological phases in driven (Floquet) systems of strongly interacting bosons, with finite-dimensional site Hilbert spaces, in two spatial dimensions. The construction proceeds by introducing exactly soluble models with chiral edges, which in the presence of many-body localization (MBL) in the bulk are argued to lead to stable chiral phases. These chiral phases do not require any symmetry, and in fact owe their existence to the absence of energy conservation in driven systems. Surprisingly, we show that they are classified by a quantized many-body index, which is well defined for any MBL Floquet system. The value of this index, which is always the logarithm of a positive rational number, can be interpreted as the entropy per Floquet cycle pumped along the edge, formalizing the notion of quantum-information flow. We explicitly compute this index for specific models, and show that the nontrivial topology leads to edge thermalization, which provides an interesting link between bulk topology and chaos at the edge. We also discuss chiral Floquet phases in interacting fermionic systems and their relation to chiral bosonic phases.